Interview Questions

isSubsequence.js

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isSubsequence = function(s, t) {
    if(!s.length) {
        return true;
    }
    let threads = [];
    for (var i = 0; i < t.length; i++) {
        if (t[i] === s[0]) {
            threads.push(t[i]);
        }
        for (let j = 0; j < threads.length; j++) {
            if(t[i] === s[threads[j].length]) {
                threads[j] += t[i];
                if (threads[j].length === s.length) {
                    return true;
                }
            }
        }
    }
    
    return false;
};

sortCharactersByFrequency.js

var frequencySort = function(s) {

    let charCounts = {};
    
    for(let i = 0; i < s.length; i++) {
        if(charCounts[s[i]]) {
            charCounts[s[i]] += 1;
        } else {
            charCounts[s[i]] = 1;
        }
    }
    
    let freqs = Object.keys(charCounts);
    
    freqs.sort((a,b) => {
      return charCounts[b] - charCounts[a];
    })
    
    freqs = freqs.map(item => {
      let accumulator = '';
      for(i = 0; i < charCounts[item]; i++) {
        accumulator += item;
      }
      return accumulator;
    });
    
    return freqs.join('')
    
};